A friend is a marine specialist here in Australia and said that for off shore marine applications, only the Cole Hershee contactors are approved  because they are mission critical.  Much  more expensive than the el cheapo auto store contactor I was replacing, but even the auto store guys advocated these units for experimental aircraft because the quality standards are so much higher.   The auto stores stocks both types, but many commercial  truck customers (we have many in town) will only use Cole Hershee.  Made in the UK, I believe.

Fred Moreno